Analytics systems allow a customer (e.g., a content provider) to monitor and assess various types of performance. For example, the customer may have a campaign in which content items are distributed for display on a resource (e.g., providing advertisements on a website). The analytics system may allow the customer to measure and assess performance of the distributed content items (e.g., by generating an analytical report). In this context, a “report” is defined as a combination of keys and values. Typically, a data element needs to include all of the keys and values associated with a report to be included in the report.